Low-carbon equivalent high strength and toughness cast steel

[0031] Example 1

[0032] A low carbon equivalent high strength and toughness cast steel, its preparation method includes the following smelting, pouring and heat treatment, and its specific process flow and process parameters are:

[0033] (1) Smelting process

[0034] Smelt in a 7-ton electric arc furnace, select dry, oil-free and less rusty Q235 steel plate (Cr0.28%, Cu0.06%) scrap 6500Kg for smelting. When the scrap steel is melted and the temperature is 1541℃, sample No. 1 , Measured C0.55%, Ni0.25%, Mo0.08%, P0.037%. Add 35Kg of electrolytic nickel, 23Kg of FeMo60-A molybdenum-iron alloy, and then blow oxygen to decarburize. During the decarburization process, the slag is continuously released and new slag is produced. Observe the flame and furnace atmosphere. Take sample No. 2 (C0.31%, Ni0.79%) , Mo0.27%, P0.009%). When the temperature is 1595℃, add FeSi75Al0.5-A ferrosilicon 20Kg alloy for pre-reduction, continue to heat up, when the temperature reaches 1680℃, remove clean slag and transfer to the shaker. The shaker requires no residual steel, residue, and baking. Bake for 1.5 hours;

[0035] The molten steel is transferred to the 7-ton AOD furnace, the temperature is measured at 1531℃, the aluminum ingot is heated by 40Kg, O:Ar=3:1, oxygen blowing and decarburization, after blowing, take No. 3 sample, measured C0.12%, Si0.01 %, Mn0.15%, P0.015%, S0.013%, Cr0.17%, Ni0.78%, Mo0.27%, Cu0.06%, V0.007%, Nb0.008%). The C content is at the lower limit, the slag is poured down the furnace body, and FeMn78C0.2 ferromanganese 100Kg, FeSi75Al0.5-A ferrosilicon 38Kg, FeCr55C0.25 ferrochrome 20Kg, FeNb60-A ferro-niobium 3.5Kg and 150Kg lime are added, and the furnace is shaken. The body was stirred for 5 minutes, and the temperature was measured at 1633℃ by tilting the furnace. Sample No. 4 was taken. The measured C0.13%, Si0.40%, Mn1.15%, Cr0.43%, Ni0.76%, Mo0.27%, P0 .017%, S0.012%, Nb0.037%, Cu0.06%, add FeV50-A ferro-vanadium 3.5Kg, shake the furnace body and stir for 1 minute, take No. 5 sample, measured C0.13%, Si0. 40%, Mn1.15%, Cr0.43%, Ni0.76%, Mo0.27%, P0.017%, S0.012%, V0.028%, Nb0.037%, Cu0.06%, balance It is Fe, and then tap the molten steel to the bottom of the ladle, measure the temperature at 1585℃, to the casting area, align the gate, let it stand for 5 minutes, and pour the casting.

[0036] (2) Heat treatment process

[0037] Heat treatment equipment: SX-10-13 high temperature box type resistance furnace

[0038] The process of high temperature normalizing is to keep at 940-960℃ for 6 hours and then cool in air;

[0039] The quenching process is water-cooled after holding at 920-940℃ for 6 hours;

[0040] The tempering process is kept at 630-650℃ for 7 hours and then cooled in air;

[0041] Through the above process, the prepared low-carbon equivalent high-strength and toughness cast steel is ZG15CrNiMnMoNb, and the weight percentage composition of the elements contained in it is: C0.13%, Si0.40%, Mn1.15%, Cr0.43%, Ni0.76% , Mo0.27%, P0.017%, S0.012%, V0.028%, Nb0.037%, Cu0.06%, the balance is Fe. The carbon equivalent is Ce=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15=0.522.

[0042] The mechanical properties of the low-carbon equivalent high-strength and toughness cast steel ZG15CrNiMnMoNb of this embodiment are: tensile strength 725Mpa, yield strength 615Mpa, elongation 23%, section reduction rate 64%, impact absorption energy (-40°C): 80, 51, 72J . From the above data indicators and figure 1 It can be seen from the metallographic structure diagram after heat treatment that the alloy cast steel meets the requirements of support shaft castings.

[0043] Example 2

[0044] A low carbon equivalent high strength and toughness cast steel, its preparation method includes the following smelting, pouring and heat treatment, and its specific process flow and process parameters are:

[0045] (1) Smelting process

[0046] Smelt in a 7-ton electric arc furnace, select dry, oil-free and rust-free Q235 steel plate (Cr0.28%, Cu0.07%) scrap 6500Kg for smelting. When the scrap steel is melted and the temperature is 1534℃, sample No. 1 is taken , Measured C0.56%, Ni0.14%, Mo0.04%, P0.033%. Add 46Kg of electrolytic nickel plate and 24Kg of FeMo60-A molybdenum-iron alloy, and then blow oxygen to decarburize. During the decarburization process, slag is continuously released and new slag is produced. Observe the flame and furnace atmosphere. Take sample No. 2 and measure C0.35%, Ni0 .80%, Mo0.24%, P0.007%. When the temperature is 1600℃, add FeSi75Al0.5-A ferrosilicon alloy 20Kg for pre-reduction, and continue to heat up. When the temperature reaches 1690℃, remove clean slag and transfer to the shaker. The shaker requires no residual steel, residue, and baking. 2 hours;

[0047] The molten steel is transferred to the 7-ton AOD furnace, the temperature is measured at 1556℃, the aluminum ingot is heated by 20Kg, O:Ar=3:1 oxygen blowing and decarburization, after blowing, take No. 3 sample, the measured C0.14%, Si0.01 %, Mn0.25%, P0.012%, S0.007%, Cr0.15%, Ni0.80%, Mo0.24%, Cu0.07%, V0.007%, Nb0.008%. Pour slag under the furnace body, add FeMn78C0.2 ferromanganese 94Kg, FeSi75Al0.5-A ferrosilicon 43Kg, FeCr55C0.25 ferrochrome 33Kg, FeNb60-A ferro-niobium, FeMo60-A ferro-molybdenum alloy 5Kg to increase ferromolybdenum content and 150Kg lime , Shake the furnace body and stir for 5 minutes, tilt the furnace to measure the temperature of 1627 ℃, take No. 4 sample, measured C0.18%, Si0.50%, Mn0.95%, Cr0.53%, Ni0.79%, Mo0. 27%, P0.016%, S0.009%, Nb0.045%, Cu0.07%, the balance is Fe; because the alloy composition of manganese does not meet the required range, add FeMn78C0.2 manganese iron 13Kg, aluminum ingot 20Kg shake Start the temperature and stir for 3 minutes, turn the furnace to measure 1631℃, take No. 5 sample, measured C0.18%, Si0.50%, Mn1.07%, Cr0.57%, Ni0.79%, Mo0.27% , P0.016%, S0.009%, V0.03%, Nb0.045%, Cu0.07%, the balance is Fe; the chemical composition is qualified. Add FeV50-A ferro-vanadium 3.5Kg, shake the furnace body and stir for 1 minute, take No. 6 sample, measured C0.18%, Si0.50%, Mn1.06%, Cr0.59%, Ni0.79%, Mo0 .27%, P0.016%, S0.009%, V0.03%, Nb0.045%, Cu0.07%, the balance is Fe. Then, the tapping liquid is poured into the bottom ladle, and the temperature is measured at 1573°C, to the casting area, align with the gate, and let it stand for 3 minutes to cast the casting.

[0048] (2) Heat treatment process

[0049] Heat treatment equipment: SX-10-13 high temperature box type resistance furnace

[0050] The process of high temperature normalizing is to keep at 940-960℃ for 6 hours and then cool in air;

[0051] The quenching process is water-cooled after holding at 920-940℃ for 6 hours;

[0052] The tempering process is kept at 630-650℃ for 7 hours and then cooled in air;

[0053] Through the above process, low carbon equivalent high strength and toughness cast steel ZG15CrNiMnMoNb can be prepared, and the weight percentage composition of the elements contained in it is: C0.18%, Si0.50%, Mn1.06%, Cr0.59%, Ni0.79%, Mo0.27%, P0.016%, S0.009%, V0.03%, Nb0.045%, the balance is Fe. The carbon equivalent is Ce=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15=0.577.

[0054] The low carbon equivalent high strength and toughness cast steel of this embodiment is ZG15CrNiMnMoNb, and its mechanical properties are: tensile strength 790Mpa, yield strength 680Mpa, elongation 20%, section reduction rate 57%, impact absorption work (-40°C): 52, 57, 49J. From the above data indicators and figure 2 It can be seen from the metallographic structure diagram after heat treatment that the alloy cast steel meets the requirements of support shaft castings.

[0055] Example 3

[0056] A low carbon equivalent high strength and toughness cast steel, its preparation method includes the following smelting, pouring and heat treatment, and its specific process flow and process parameters are:

[0057] (1) Smelting process

[0058] Smelting in a 7-ton electric arc furnace, selecting dry, oil-free and rust-free Q235 steel plate (Cr0.28%, Cu0.06%) scrap 6500Kg for smelting, when the scrap steel is melted and the temperature is 1545℃, sample No. 1 , Measured C0.56%, Ni0.13%, Mo0.06%, P0.029%. Add 42Kg of electrolytic nickel and 23Kg of FeMo60-A molybdenum-iron alloy, and then blow oxygen to decarburize. During the decarburization process, the slag is continuously released and new slag is produced. Observe the flame and furnace atmosphere. Take sample No. 2 (C0.29%, Ni0.79%) , Mo0.26%, P0.005%). When the temperature is 1603℃, add FeSi75Al0.5-A ferrosilicon 20Kg alloy for pre-reduction, and continue to heat up. When the temperature reaches 1695℃, remove clean slag and transfer to the shaker. The shaker requires no residual steel, residue, and baking. Bake for 1.5 hours;

[0059] The molten steel is transferred to the 7-ton AOD furnace, the temperature is measured at 1538℃, the aluminum ingot is added 40Kg and the temperature is increased, O:Ar=3:1 oxygen blowing and decarburization, after blowing, take No. 3 sample, the measured C0.12%, Si0.01 %, Mn0.19%, P0.014%, S0.013%, Cr0.20%, Ni0.78%, Mo0.25%, Cu0.06%, V0.007%, Nb0.008%). The C content is at the lower limit, the slag is poured down the furnace body, and FeMn78C0.2 ferromanganese 100Kg, FeSi75Al0.5-A ferrosilicon 38Kg, FeCr55C0.25 ferrochrome 24Kg, FeNb60-A ferro-niobium 3.5Kg and 170Kg lime are added, and the furnace is shaken. The body was stirred for 5 minutes, and the temperature was measured at 1637℃ by tilting the furnace. Sample No. 4 was taken. The measured C0.14%, Si0.42%, Mn1.17%, Cr0.49%, Ni0.76%, Mo0.24%, P0 .015%, S0.010%, Nb0.040%, Cu0.06%, add FeV50-A ferrovanadium 3.5Kg, shake the furnace body and stir for 1 minute, take No. 5 sample, measured C0.14%, Si0. 38%, Mn1.15%, Cr0.50%, Ni0.76%, Mo0.24%, P0.015%, S0.010%, V0.025%, Nb0.040%, Cu0.06%, balance It is Fe, and then tap the molten steel to the bottom of the ladle, measure the temperature at 1580℃, to the casting area, align the gate, let it stand for 4 minutes, and pour the casting.

[0060] (2) Heat treatment process

[0061] Heat treatment equipment: SX-10-13 high temperature box type resistance furnace

[0062] The process of high temperature normalizing is to keep at 940-960℃ for 6 hours and then cool in air;

[0063] The quenching process is water-cooled after holding at 920-940℃ for 6 hours;

[0064] The tempering process is kept at 630-650℃ for 7 hours and then cooled in air;

[0065] Through the above process, the low carbon equivalent high strength and toughness cast steel prepared is ZG15CrNiMnMoNb, and the weight percentage composition of the elements contained in it is: C0.14%, Si0.38%, Mn1.15%, Cr0.50%, Ni0.76% , Mo0.24%, P0.015%, S0.010%, V0.025%, Nb0.040%, Cu0.06%, the balance is Fe. The carbon equivalent is Ce=C+Mn/6+(Cr+Mo+V)/5+(Ni+Cu)/15=0.543.

[0066] The mechanical properties of the low-carbon equivalent high-strength and toughness cast steel ZG15CrNiMnMoNb of this embodiment are: tensile strength 735Mpa, yield strength 620Mpa, elongation 23%, section reduction rate 63%, impact absorption energy (-40°C): 80, 51, 72J . From the above data indicators and image 3 It can be seen from the metallographic structure diagram after heat treatment that the alloy cast steel meets the requirements of support shaft castings.

[0067] The test equipment used in the above three embodiments is SX-10-13 high temperature box-type resistance furnace; universal material testing machine, model: WE-30.

[0068] The dimensions of the tensile bar and impact test block used in the above three embodiments are: according to ASTME8, the diameter of the tensile test bar is 12.5mm, and the gauge length is 50mm for 4d; the chuck is Ф28mm, and the total length of the test bar is 143mm. The size of the impact sample is 10×10×55mm.

[0069] The above three embodiments all introduce microalloying technology into the production of low-carbon cast steel, which greatly improves the material strength and low-temperature toughness while maintaining good welding performance, and fully meets the needs of the support shaft of the key parts of the mining vehicle.